Lecture quiz 9                             

Write a C program equivalent to one of the C programs in sections 1.5 of K&R. The 
programs are called file copying, character counting, line counting, word counting, 
and arrays. They are described on pages 15 to 24 of K&R (or see programs 10, 11 and 
13 to 17 at http://www.temple.edu/stafford/cis2107f12/kandr/chap1/index.html

   #include <stdio.h>
   int strcmp(char s[], char t[]);
   main() {
      char s[] = "This is the first string";
      char t[] = "This is the second string";
      printf("%d\n", strcmp(s, t));
   }
   int strcmp(char *s, char *t) {
      for  (; *s == *t; s++, t++) 
         if (*s == '\0')
            return 0;
      return *s - *t;
   }

   #include <stdio.h>
   int strcmp(char s[], char t[]);
   main() {
      char s[] = "This is the first string";
      char t[] = "This is the second string";
      printf("%d\n", strcmp(s, t));
   }
   int strcmp(char *s, char *t) {
      int i;
      for  (i = 0; *(s+i) == *(t+i); i++) 
         if (*(s+i) == '\0')
            return 0;
      return *(s+i) - *(t+i);
   }

   #include <stdio.h>
   int strcmp(char s[], char t[]);
   main() {
      char s[] = "This is the first string";
      char t[] = "This is the second string";
      printf("%d\n", strcmp(s, t));
   }
   int strcmp(char *s, char *t) {
      while (*s == *t) {
         if (*s == '\0')
            return 0;
         s++, t++;                        
      }
      return *s - *t;
   }

How to get intro trouble.

   1. (*s == *t) != '\0'
      (*s == *t) && (*s != '\0')

   2. (*s = *t) 

   3. while (*s++ == *t++)

   4. while (++*s == ++*t) 
   
   5. return s - t;